This disclosure is directed to a digital to analog (D/A) converter with current mode output. The device of this disclosure will accept a binary word and convert it to a current flowing into the output of the device. The magnitude of the current will be directly proportional to the magnitude of the input code.
In the past D/A converter circuits operating on the current mode would accept a binary word and first convert it into a voltage. This voltage would then normally be applied to an operational amplifier whose output would then be used to control the conduction of a transistor so that current is allowed to flow from a load through the transistor and into a resistor creating an IR drop. The voltage developed would then be compared with the input voltage with the circuit stabilizing when the voltages were zero.
While the prior art D/A converter circuits work well for non-zero values of current, they exhibit shortcomings at very low current levels. The present disclosure overcomes the problem of near zero current operation while also preferably including a current multiplying feature and allowing the use of simple low cost components.